Contents

Spaceships

The first c/4 orthogonal spaceship, 119P4H1V0 was discovered by Dean Hickerson in December 1989. Hickerson then found a small tagalong for this spaceship which could be attached in two different ways. These three spaceships were the only known c/4 orthogonal spaceships until Hartmut Holzwart discovered 163P4H1V0 in July 1992. The searches conducted by Holzwart also turned up the first method of creating arbitrarily large c/4 orthogonal spaceships by repeatedly attaching a tagalong to the back of 103P4H1V0. Holzwart also found the first orthogonal non-monotonic spaceship, non-monotonic spaceship 1, during this search. In May 1996Tim Coe discovered 46P4H1V0, which was the smallest known spaceship of this speed until April 2012, when Josh Ball discovered 37P4H1V0. From February to March 2006, Hartmut Holzwart found several ways to create c/4 orthogonal greyships.

The first higher period c/4 orthogonal spaceship was discovered by David Bell in September 2000. It had a period of 20 and consisted of a blockpuffer found by Jason Summers and a side sparker used to delete the blocks. In the following month Summers found period 8 and 12 spaceships based off of a failed blinker puffer and a spaceship with a forward domino spark. Several other periods were achieved by perturbing the output of a period 168 puffer discovered by Paul Tooke in November 2003.

Puffers

Jason Summers found the first c/4 orthogonal puffer, which had period 9732 and was extremely dirty, in January 1999. In November 2003 Paul Tooke discovered a versatile period 168 puffer the output of which could be perturbed by sparkers to produce puffers of lower periods.

Rakes

The lowest period c/4 orthogonal rakes are based on Paul Tooke's p168 puffer. A method of rake construction is also known for all periods above about 800.

Wickstretchers

c/4 orthogonal was the first speed known to contain a wickstretcher, wickstretcher 1. It was discovered by Hartmut Holzwart in October 1992 and stretched ants from an ant stabilizer found by Dean Hickerson.